Tolerance Limits for Surface Errors of Plates for Reflection Echelon

Expressions have been obtained for the intensity distribution of the fringes in the reflection echelon in the presence of surface errors on the plates. The errors considered are the ones arising during the polishing process, due to inhomogeneous reflection coating, and due to the residual curvature of the plates. These expressions have been utilized for the evaluation of the intensity distribution in a reflection echelon consisting of 20, 30, 40 and 50 plates. Hence permissible errors on the surfaces of the echelon plates have been obtained and it has been confirmed that in order to take full advantage of number N of the plates, surface errors should not exceed 1/4 N of a wavelength in the middle of the visible spectrum.     

Evaluation of Errors in Calibration Procedures for Measurements of Reflection Coefficient

Procedures for the calibration of computer-controlled network analyzers in reflection measurements are studied. The major aim of this paper is to develop an error analysis in order to define a quality factor, for evaluating the performances of a calibration procedure. This is done by using the invariance property of the cross ratio, which easily lets one obtain analytical expressions for the residual errors As an application of this technique, a comparison between two actual calibration procedures has been made using an automatic network analyzer. The experimental results favorably compare with the ones obtained on theoretical basis.     

基于L-M算法的二维PSD非线性校正

本文分析了二维PSD的工作原理及非线性产生的原因，提出了应用BP神经网络对PSD非线性进行修正的方法。由于传统的BP及其改进算法收敛速度过慢，往往收敛于局部极小值等缺点。因此引入了L—M算法。本文通过利用MATLAB工具箱进行BP网络的建立、训练、仿真。结果证明了L—M算法不仅提高了测量精度，而且缩短了训练时间。     

Correction of Systematic Errors Due to the Voltage Leads in an AC Josephson Voltage Standard

The National Institute of Standards and Technology (NIST) has recently reported the first application of a quantum ac Josephson voltage standard for the calibration of thermal transfer standards in the 1- to 10-kHz frequency range. This paper describes preliminary work on extending its frequency calibration range up to 100 kHz by correcting the systematic errors due to voltage leads. A ground loop created by the dc blocks, which is a previously unaccounted source of high-frequency systematic error, has been identified, and its effects are partially mitigated.      

Method for Compensating Heat Flux Errors in Mini-TPW Cell Measurements

Small triple-point-of-water cells (mini-TPW) are used in laboratories to monitor the stability of PRTs. Compared with a standard TPW cell, heat flow in the thermometer well usually disturbs the apparent equilibrium temperature to a larger extent in a mini-TPW cell due to its smaller dimensions. In this paper, the heat flow effect is studied on the basis of experimental data. Special attention is paid to the thermal conduction along a thin thermometer probe and to the self-heating of the probe. A new method for compensating the error due to the heat flow is presented. It is shown that the compensated results are in good agreement with results obtained with standard TPW cells. The determined differences were well within the estimated expanded uncertainty of 2 mK (k = 2). The heat flow effect was studied experimentally by controlling the temperature of the upper part of a PRT inserted in a mini-TPW cell. Also, the effect of different fillings of the measurement well of the cell was studied. Without the compensation, thin metal-sheathed PRTs (1.6 and 2.2 mm) indicated 3 to 9 mK differences between mini-TPW and standard TPW cells.     

A Graphical Method for Calculating Reflection Errors in Radiation Thermometry

This article presents a graphical method to calculate reflection corrections for radiation thermometry. The method is based on the observation that the measured radiance of a target is a linear combination of radiances dependent on the emissivity of the target. The method is most easily implemented as a nomogram, enabling thermometer users to estimate reflection corrections immediately when measurements are taken. The nomogram also provides a visual means of explaining the impact of reflection errors on measurements and for explaining the impact of measurement uncertainties on temperature measurements corrected for reflections.     

Systematic Errors in Measurements of the Optical-Ranging Characteristics of Small Objects with Nonlocal Coherent Reflection

Measurement Techniques - Adjustments in the phase structure of optical radiation reflected from a small object with nonlocal coherent reflection and detected by an objective with spherical...     

Polarization Beam Splitting in Optical Fibre Couplers Due to Form Birefringence

Abstract

Polarization dependent corrections to the scalar coupling coefficients of the fundamental modes on two identical optical fibres are calculated from scalar supermode fields corrected up to first order in weak coupling. The method applies to arbitrary refractive-index profiles.     

自动修正拍摄俯仰误差的鱼眼图像校正方法

现有鱼眼图像校正法仅针对单幅图像,无法提供足够信息来自动修正由于相机抖动或环境干扰等因素造成的形变误差.本文利用图像拼接时的特征点,计算出待拼接图像之间几何变换关系,进而准确估计出图像的俯仰角度,基于此提出了一种精确校正鱼眼图像的方法.该方法的主要特点能恢复校正图像的垂直不变性,增强校正图像之间的对齐程度,使得全景拼接中变换矩阵求解变得更为简单,增强融合效果.实验证明,本文校正算法可以消除由于形变误差造成的图像拼接中的重影,增强拼接图像的效果.     

Reflection/transmission Measurements of Anisotropic Films with One of the Principal Axes in the Direction of Columnar Growth

Abstract

In depositing crystalline thin films, anisotropy may be induced by the texture structure of the film. Generally one of the principal axes of this anisotropy is in the direction of columnar growth, which may be neither normal nor parallel to the film surface. In this paper we have developed a general method for characterizing thin films with this kind of anisotropy. Propagation of plane waves in media with the above mentioned crystalline structure has been studied. The reflectance and transmittance of a plane wave from the films with the structure-induced anisotropy have been calculated. By comparing calculations with measurements, we could determine optical properties and thicknesses of the films with the columnar-structure-induced anisotropy.     

用加权残数法分析各向异性层合薄板的几何非线性问題

各向异性层合薄板的几何非线性问题,由于控制方程和边值问题求解的复杂性,历来解法繁杂,工作量大且存在较大局限性。本文利用加权残数法简捷,有效的特点,提出以具有良好拟合性和对边界条件灵活可适性的五次B—样条基函数的组合作为试函数基底,然后采用阻尼最小二乘法,应用于解决这类复杂问题。本文在计算时编制了较为通用的程序,若干具体算例表明,本方法收敛稳定,结果准确,且解法简捷,统一,便于程序标准化与推广应用。     

Photoelastic Analysis of Dynamic Stresses in Anisotropic Plates

The formulas for the correct evaluation of dynamic stresses in structurally anisotropic plates are deduced by using the polarization-optical method and the basic relations of photoelasticity. We study the wave field of stresses formed in an anisotropic plate loaded on its free boundary by pulses from a point source and the influence of anisotropy on the character of the analyzed field. The distribution of dynamic stresses induced by a concentrated source is investigated and the dependences of the maximum stresses in quasilongitudinal -waves and Rayleigh waves on the distance from the source are established.     

基于贝叶斯模型的动态误差实时修正方法研究

应用贝叶斯动态模型理论,探讨了非平稳动态测量误差贝叶斯建模原理及实时修正的方法.由多项式模型、季节模型、回归模型和噪声模型等模型分量组合的贝叶斯动态模型,较好地描述了各种系统误差和随机误差的综合特征,客观反映了动态测量误差的变化规律.利用贝叶斯递推算法和标准信号插入,适时对动态误差模型参数进行调整,以适应非平稳动态误差的时变性,有效控制了动态模型预报精度损失,提高了动态误差实时修正的精度.通过长光栅动态测量系统实时误差修正实例,验证了该方法正确可行,误差修正效果显著,具有较高的应用价值.     

Asymmetry in the Diffraction Pattern of a Grating Due to Periodic Errors

The effect of diffraction grating errors of low spatial frequency is investigated numerically and analytically.     

Error in Insertion Loss Measurement Due to Multiple Reflections

A system error of a waveguide impedance bridge due to multiple reflections between the test section and the bridge circuit is analyzed. A principle and a method of making corrections to this system error are presented with actual numerical examples.     

12Bit量化误差对正弦参数拟合影响的误差界

针对12 Bit量化误差对四参数正弦拟合带来的误差影响，分别在有效位数、幅度、频率、初始相位和直流分量五项参数上进行了拟合误差界的搜索。选取的条件变量分别是幅度、序列所含波形的周波数、初始相位、直流分量以及序列数据点数。以两两联动的双条件组合方式进行误差界搜索，获得了上述五项参数的误差界随不同条件变化而变化的曲线规律，筛分出了显著影响量和不显著影响量，以及明确的误差上界和下界。该结果可用于拟合参数的误差和不确定度估计，也可以在设定拟合误差和不确定度情况下，选择测量条件。     

Particular Cases of the Calculation of the Errors (Uncertainties) of the Results of Direct Measurements with Multiple Observations

It is shown that an expression for the total error as defined in GOST 8.207-76 of the corrected results of a measurement possesses an anomaly when this error is less than one of its components, and that a similar anomaly occurs for the expanded uncertainty as defined in MI 2552-99. The error of uncorrected results of a measurement whose random component is distributed according to different laws is compared with calculations utilizing RD 50-453-84 and MI 1788-87.     

Standardizing the Errors of Indirect Measurements with Constriction-Type Variable-Pressure Flowmeters

The relative and absolute measurement errors are examined for devices using constrictions operated under various conditions. The practical metrology of indirect measurements can be based on a principle of equal absolute errors at the boundaries of the measurement range.     

精确修正光电经纬仪中的系统误差方法研究

对运动目标进行精确的轨道测量是光电经纬仪的首要任务。在此 ,探讨了一种高精度的系统误差修正方法——球谐函数修正法 ,并将该方法运用于光电经纬仪中对系统误差进行修正 ,获得了比较满意的结果。